Color-producing tube having screen containing plurality of birefringent materials



ESO'NQOQ ALW/v A. SNA/DER SCREEN CONTAINING PLURALITY S L u@ R6 E m uw PMl. A .nl N w Smm@ w Anm@ Q AFM m1.. HE ,J Amn n. BBF .k wp s r E, m mwb w w w of w c U wf 3 R ..1 y M M Al\ O D. n QOL 6o 1 9C 1. Q j 2 E V..M .J H M COLOR-PRODUCING TUBE HAVING SCREEN CONTAINING PLURALITY OFBIREFRING- ENT MATERIALS Alvin A. Snaper, 9722 Casalia Ave., Chatsworth,Calif. 91311 Filed Oct. 1l, 1965, Ser. No. 494,689 1 Claim. (Cl. 313-91)ABSTRACT' 0F THE DISCLQSURE The present invention is concerned withproducing an output -beam of light whose color is determined by thepoint at which an electron beamis incident on a phosphor layer. An`'embodiment of the invention includes two parallel differently polarizedlayers between which is sandwiehed a layer of birefringent material, theparticular color of the output beam corresponding to the characteristicsof either the birefringent material or the polarized layer, or both,behind the phosphor layer whereat the electron beam strikes it.

The present invention relates-in general to apparatus for producing anddisplaying colors andvcolor patterns in response to electron beams andmore particularly relates to apparatus of the kind mentioned in whichpolarized and birefringement materials are used and form an essentialpart of the apparatus.

At the present time, different phosphorsare used to convert an electronbeam to respectively different colors. This is true, for example, in acolor television tube where tri-color phosphors are deposited in a dotpattern or mosaic on the face of the tube, the color or combination ofcolors visi-bly appearing in any area of the tubes face at any one timebeing determined by which of the phosphors are being struck by anelectron beam at that time. One of the problems involved in the use ,ofphosphors is that the phosphors eventually-erode orde'teriorate inquality, with the result that the colors also eventually `deterioratefrom their original brightness and sharpness. In addition, phosphors ofdifferent color response have different chemical,l electrical andphysical properties which makes it necessary in color phosphor cathoderay tubes to adjust the system output to the lowest efficiency phosphorin order to obtain coior balance. This is normally accomplished bydowngrading or'reducing the output of the more eliicient phosphors .tothe level of the least efficient. Note-red is usually the least eicient.A further ditiiculty encountered in connection with this prior techniqueis that phosphors are, relatively speaking, not easy to handle or,stated differently, to work with, and, therefore, their use requires theapplication of special procedures which, in turn, increases the cost ofsuch tubes.

The present invention substantially eliminates these prior artdisadvantage by entirely eliminating the requirement for phosphormaterials as the primary source of color, and it does so by making useof the phenomenon that colored light is obtained when ordinary whitelight is successively subjected to the processes of polarization andbirefringence. More particularly, the present invention is based on theconcept that white light passing through a polarizing plate, then a-birefringent material of uniform characteristics andthereafter viewedthrough an analyzing polarizer, can be made to produce any color of thespectrum, which portion of the spectrum being dependent upon andcontrolled by either the specific bireringent materialchosen, itsthickness, its uniform strain characteristics, the angle of polarizationof the analyzer, or combinations thereof.

Based on this concept, a first embodiment of the invented States Patenttion is provided with a sandwich arrangement of 4 layers, namely, awhite phosphor layer followed by a pair of differently polarized layersbetween which is located a layer made up of materials havingrespectively different birefringence qualities. As is well known, whitephosphor has the quality of producinga beam of white light when a streamof electrons is incident thereon. Accordingly', different colors may beobtained by directing an electron beam toditferent areas on the whitephosphor layer. In other embodiments, instead of using a layer Ymade upof different birefringent materials, the same results are obtained byusing instead the same birefringent material' throughout the layer buteither varying the thickness of the material at different points thereonor varying the plane of polarization over different areas of the outerpolarizing layer. Finally, ina last embodiment that is especiallyadapted for use in a television tube or the like, a mosaic ofbirefringent material having diverse birefringent qualitiescorresponding to the desired three-color output is used. In thisembodiment, an aperture mask corresponding to and in registration withthe mosaic is also employed, the several-electron beams beingsimultaneously and selectively directed through the holes in the mask toproduce the desired colored pattern.

It is, therefore, an object of the present invention to provideelectron-beam apparatus that facilitates the production of visual colordisplays and that is more versatile in terms of its possibleapplications than prior equipment of this kind.

It is another object of the present invention to provide apparatus forproducing color in response to the impingement of an electron beam thatis less expensive, less diicult to manufacture, and more eicientrelative to existing apparatus.

It is a further object of the present invention to provide apparatus forproducing color in response to the impingement of an electron beamwithout the use of colorproducing phosphors.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objects and advantages thereof, will be better understoodfrom the following description considered in connection with theaccompanying drawing in which several embodiments of the invention areillustrated by way of example. It is to be expressly understood,however, that the drawing is for the purpose of illustration anddescription only and is not intended as a denition of the limits of theinvention.

FIGURE l is a cr0sssectional view of a rst embodiment of the inventionin which the birefringent layer is made up of a number of differentmaterials having correspondingly different birefringent qualities;

FIGURE 2 illustrates a modification of the' FIG. l embodiment in whichthe birefringent layer is made up of the same material throughout but ofseveral different thicknesses to provide the different birefringementeffects;

FIGURE 3 illustrates still another modification of the FIG. l embodimentin which the qualities of the polarizing material are varied rather thanthe birefringent material;

FIGURE 4 is lan exploded view in cross-section of another embodiment ofthe present invention in which a biretringent dot screen and aperturemask are utilized; and

FIGURE 5 is a perspective view that illustrates how the FIG. 4 apparatusmay be extended to provide a structure that is suitable for use iritubes of the color-television type.

For a consideration of the invention in detail, reference is now made tothedrawing wherein like or similar parts or elements are given like orsimilar designations throughout the several figures. In FIG. l, theembodiment is shown to basically include a multi-layered formation ofmaterials placed in face-to-face relationship to form a sandwicharrangement of them. More specifically, it includes a pair of inner andouter polarizing layers 10 and 11, respectively, a birefringent layer 12positioned between the polarizing layers and a white phosphor layer 13deposited on the front face of polarizing layer 10. Although notessential, layers 10 and 11 are preferably cross-polarized with respectto each other. Regarding these polarizing layers, there are many wellknown materials that can be used, such as Polaroid, the trade name of amaterial in sheet .form usually consisting of oriented crystals ofherapathite on or in a transparent base or carrier. The patent to R. W.Weeks et al., Patent No. 2,983,824, discloses this fact at column 3,lines 38- 41 thereof. However, by way of further example, suitablyoriented crystal film layers of iodoquinine sulfate may also be used. Asfor layer 12, it is made up of two or more materials having respectivelydifferent birefringence characteristics or qualities that respectivelyoccupy different areas or portions of the layer. Layer 12 in FIG. lillustratively includes three different birefringent materials that arerespectively designated 12a-12e. Many different transparent materials,such as polymerized ethylene, (CZHQH, commonly known as polyethylene,exhibit the quality of birefringence and may be used herein in layer 12.Some other common materials that are satisfactory for application hereinare Celluloid, which is a proprietary product consisting basically of asolid solution of celiulose nitrate and a plasticizer, cellulose acetatebutyrate, and Cellophane, which is a form of cellulose acetate.Furthermore, many inorganic and organic crystals exhibit this quality ofbirefringence. Examples of the inorganic kind are calcite calciumcarbonate, a common mineral, and quartz oxide of silicon, another commonmineral. The described sandwich or panel arrangement of layers 10-13requires an electron beam for its operation and, therefore, it isnormally mounted i1 a cathode-ray type of tube with phosphor layer 13facing the tubes electron gun. However, since cathode-ray tubes arestandard items, for sake of clarity and expediency such a tube is onlyschematically represented here by an electron-beam source 14.

In operation, when the electron beam produced by source 14 is directedagainst white phosphor layer 13 in a region thereof that facesbirefringent material 12a, such as beam 14a, a corresponding beam ofwhite light is generated by the phosphor at the point of incidence thatpasses through polarizing layer 10 to birefringent layer 12.Accordingly, the light reaching layer 12 is plane polarized. At thispoint, various components of the light beam are impeded or shifted inphase by material 12a, with the result that only a spectral portion ofthe light is allowed to pass through outer polarizing layer 11, therebyproducing a color output 15a by what may be termed subtractive filteringof the white light input. The actual color of output light 15a isdetermined by the particular composition and characteristics ofbirefringent material 12a. By directing the beam to other regions ofphosphor layer 12, as illustrated by beams 14b and 14C, still othercolors may be obtained. Thus, for the reasons previously explained, anelectron beam 14b ultimately results in an output beam of light 15bwhose color is determined by the composition and characteristics ofbirefringent material 12b and an electron beam 14e` likewise causes anoutput beam of light 15e to be produced whose color is determined by thecomposition and characteristics of birefringent material 12C. Since, aswas previously mentioned, materials 12a-12e are of different compositionand, therefore, have correspondingly different birefringencecharacteristics, the colors of light beams 15a-15e are likewisedifferent from one another. It will be obvious to those skilled in theart that by successively defiecting the electron beam to differentregions of phosphor layer 13 or by alternately widening and narrowingthe electron beam, different color combinations. schemes and patternsmay be displayed.

A birefringent layer of uniform thickness but of different compositionwas utilized in the FIG. l embodiment. However, the same kind of outputcolor effects can be obtained by using instead a birefritgent layer madeof the same material throughout but of different thicknesses overdifferent areas or regions thereof. Such a modification is illustratedin FIG. 2 wherein the different thicknesses of layer 12 are respectivelydesignated 12a-12c. Hence, in this case also, electron beams 14a- 14ewill respectively produce differently colored beams of light 15a-15e.

The FIG. 1 embodiment may be modified in still another way and yetproduce the s'ame o utput display of color. More specifically, insteadof employing a birefringent layer of uniform thickness and varyingcomposition or a layer of the same material throughout but of varyingthickness, a birefringent layer of uniform thickness and uniformcomposition may be used together with an outer polarizing layer whereondifferent areas or regions are differently polarized. A modification ofthis kind is illustrated in FIG. 3 wherein the birefiingent layer ofuniform composition and thickness is designated 12' and the outerpolarizing layer of varying polarization is designated 11', the threedifferently polarized regions thereon being designated 11a, 11b andll'c. Accordingly, as before, in response to the impingement of theelectron beam 14a-14C on phosphor layer 13, differently colored beams15a-15c are produced, the particular colors obtained being primarilycontrolled by the planes of polarization 11a-11c.

Although obvious, it should nevertheless be mentioned that the severaldifferent features of the FIG. l-FIG. 3 devices may also be combined toprovide output color effects. Thus, for example, in a singlearrangement, a birefringent layer made up of different compositions ofmaterial (FIG. 1) or one having regions of different thickness (FIG. 2)may also be combined with a polarizing layer having differentlypolarized areas (FIG. 3).

An exploded view of a second embodiment of the i1- vention is shown inFIG. 4 wherein a birefringent dot screen 16 is mounted betweencross-polarized layers 10 and 11 and an aperture mask 17 is mounted infront of light phosphor layer 13. More specifically, in thisernbodiment, layer 16 is made up of a large number of dots or tinyregions of birefringent material arranged in some sort of pattern ormosaic configuration, these so-called dots or tiny regions being inregistration with the holes through mask 17. Thus, the electron beamonly has access to a dot or tiny region of birefringent material byfirst passing through the'` associated mask aperture and when this isdone, a corresponding tiny beam of colored light will emerge frompolarization layer 11. The same birefringent material may be used informing the mosaic of screen 16 or, needless to say, differentbirefringent materials may be used, or a combination of both. In thefirst case, the same output color would be obtained irrespective of theorientation of the electron beam, whereas in the latter instances thecolor obtained at any time would depend on which of the mask aperturesthe beam was then being directed through. Moreover, it will berecognized from the descriptive material presented previously thatinstead of using different birefringent materials, the desired coloreffects may also be obtained through the use of a single composition ofmaterial, either by varying the thickness of the material in thedifferent dot areas' or if the same thickness is used, by providing ananalogous dot array on polarizing layer 11 in which the planes ofpolarization in the dot areas vary in accordance with the desired colorpattern.

The FIG. 4 embodiment lends itself for use in a colortelevision tube andthe manner in which it can be adapted for such use is illustrated inFIG. 5 to which reference is now made. As shown therein, a sandwich orpanel arrangement of the same layers 10, 11, 13 and 16 is mounted on theinside surface of the tubes face plate designated 18 and aperture mask17 is positioned somewhat in front of it. As is well known; televisiontube generates three basic colors from which all other color gradationsare substantially produced. Accordingly, the mosaic of dots inbirefringent layer 16 is likewise arranged to produce three differentcolors and any one of the several techniques previously mentioned may beutilized to do so.' As shown in the ligure, all tli'e dots ultimatelyproducing one color is designated by the capital letter A, thoseinstrumental in producing the second color is designated by the capitalletter B and the rest are designated by the letter C. In the fabricationof a birefringent layer for .application in a color television tube, adot pattern, of birefringent material consisting of three differentvariations corresponding to the desired three-color outputrnay beproduced by a variety of means. Thus, for example, in one manufacturingtechnique a uniform layer of birefringent plastic is embossed with aheated pattern die to produce the desired pattern in the form of threelevels of thickness, each dimension of thickness being that required toproduce a specific color when light fromy the electron beam excitedphosphor impinges thereon. It is also possible to produce a three-levelbirefringent layer by conventional means similar to those in use forstandard deposition of tricolor phosphors in which patterns of; dots aredeposited by silk screening or photographic etching means. Vapordeposition through suitable masks can also be utilized.

Although constructed differently, the operation of the FIG. 5 apparatusis basically the same as would be found in a standard television tube.Thus, when only one electron beam is directed through an aperture inmask 17 to i-mpinge on phosphor layer 13, only one of the threebirefringent dots associated with that aperture is illuminated, therebycausing only one of the three colors to be produced. On the other hand,when two electron beams are directed through the aperture, two of thebirefringent dots are illuminated and, therefore, two of the three basiccolors are produced and, as may be expected, when all three electronbeams are generated and directed through the aperture, all three colorsare produced. This last instance involving three electron beams isillustrated in FIG. 5, all three beams being shown passing through anaperture of mask 17 to impinge upon three points on the surface ofphosphor layer 13 that face an associated cluster of three birefringentdots A, B and C.

Although a number of particular arrangements of the invention have beenillustrated above by way of example, it is not intended that theinvention be limited thereto. Accordingly, the invention should beconsidered to include any and all modifications, alterations orequivalent arrangements falling within the scope of the annexed claim.

Having thus described the invention, what is claimed isz.

1. Color-,producing apparatus comprising: a sandwich arrangement oflayers including rst and second polarized layers of light-transparentmaterial having different planes of polarization, a plurality ofcoplanar birefringent layers having respectively different birefringencequalities mounted between said first and second layers, and a thirdlayer of phosphor material for producing white light in response to theincidence of an electron beam thereon; and means for producing anelectron beam and selectively directing it for impingement on differentareas of said third layer.

References Cited UNITED STATES PATENTS 2,184,999 12/1939 Land et al.350--158 2,481,622 9/1949 Rosenthal 313-91 X V2,531,823 11/1950 Murray350-158 X 2,607,272 8/1952 Bond 350-157 2,663,171 12/1953 Boone S50-158X 2,829,555 4/1958 Keston 350-157 X 2,983,824 5/1961 Weeks et al 313-91X 3,131,253 5/1964 Zandman et =al. 350-158 X 3,148,281 9/1964 Fyler-313--91 X '2,598,941 6/1952 Roth B13-92.5

ROBERT SEGAL, Primary Examiner.

